When I chop things up small, there aren't any left overs. When I throw hole things or big junks in there, it's there for days and I have to toss it over the fence.
So to prevent waste from my "picky" birds, I cook anything hard, and I cut everything up small. They REALLY like carrot peelings, but I chop those up into manageable pieces. They also enjoy whatever mush comes out of the juicer, and pepper seeds (from green/red/yellow peppers, not hot ones!)
If I give them a bowl of chopped up Bantam sized bits, it's gone in a day. If I give them whole things, they might not even touch it. So the only whole things I give them is sweet corn, they seem to enjoy pecking that.